The present invention relates to a method for producing a polymer, a polymer, an insulating-film-forming composition, a method for producing an insulating film, and an insulating film.
A silica (SiO2) film formed by a vacuum process such as chemical vapor deposition (CVD) has been widely used as an interlayer dielectric for semiconductor devices or the like. In recent years, a coating-type insulating film called a spin-on-glass (SOG) film which contains a tetraalkoxysilane hydrolysate as the major component has also been used in order to form a more uniform interlayer dielectric. Along with an increase in the degree of integration of semiconductor devices, a low-relative-dielectric-constant interlayer dielectric called an organic SOG which contains a polyorganosiloxane as the major component has been developed.
In particular, an improved electrical insulation between conductors has been demanded accompanying a further increase in the degree of integration and the number of layers of semiconductor devices. Therefore, an interlayer dielectric material has been demanded which exhibits a lower relative dielectric constant and excellent crack resistance, mechanical strength, and adhesion.
A composition containing fine particles obtained by condensing an alkoxysilane in the presence of ammonia and a basic partial hydrolysate of an alkoxysilane (JP-A-5-263045 and JP-A-5-315319), and a coating liquid obtained by condensing a basic hydrolysate of a polyalkoxysilane in the presence of ammonia (JP-A-11-340219 and JP-A-11-340220) have been proposed as low-relative-dielectric-constant materials. However, the material obtained by the above method is not suitable for production on an industrial scale, since the reaction product exhibits unstable properties and the resulting coating varies to a large extent in relative dielectric constant, crack resistance, mechanical strength, adhesion, and the like. A method of forming a low-dielectric-constant insulating film using a coating liquid prepared by mixing a polycarbosilane solution and a polysiloxane solution has also been proposed (JP-A-2001-127152). However, this method has a problem in which the carbosilane and the siloxane having nonuniform domains are dispersed in the coating.
A method has also been proposed which uses an organic silicate polymer obtained by preparing a carbon-bridge-containing silane oligomer from an organometallic silane compound and hydrolyzing and condensing the carbon-bridge-containing silane oligomer (WO2002-098955). However, the material obtained by this method cannot be stored for a long time due to the poor stability of the reaction product. Moreover, this material exhibits poor adhesion to a substrate.